An in-depth analytical approach to the mechanism of the RAFT process in acrylate free radical polymerizations via coupled size exclusion chromatography–electrospray ionization mass spectrometry (SEC–ESI-MS)

Feldermann, Achim; Toy, Andrew Ah; Davis, Thomas P.; Stenzel, Martina H.; Barner‐Kowollik, Christopher

doi:10.1016/j.polymer.2005.01.101

Cited by 85 publications

(95 citation statements)

References 50 publications

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“…[26] In this new technique, thioketones are used to reversibly trap the propagating radical as a stabilised intermediate radical (.C(SP n )(t-Bu) 2 ), and it is noteworthy that the t-Bu substituents in this new system are actually less effective radical stabilisers than the thiyl and phenyl groups in the CDB system (.C(SP n ) 2 Ph). In this light, coupled with the evidence from kinetic studies of the induction period in RAFT polymerisation, [27,28] it seems likely that the ongoing discrepancy between the slow fragmentation model and the EPR-derived radical concentrations [5] lies not in a revision of the measured K values, but rather the introduction of additional side reactions involving the RAFT-adduct radical, such as reversible termination. [29,30] Further work in this direction is now underway.…”

Section: Discussionmentioning

confidence: 99%

Is the Addition‐Fragmentation Step of the RAFT Polymerisation Process Chain Length Dependent?

Izgorodina

Coote

2006

Macro Theory & Simulations

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Summary: The chain length dependence of the addition‐fragmentation equilibrium constant (K) for cumyl dithiobenzoate (CDB) mediated polymerisation of styrene has been studied via high level ab initio molecular orbital calculations. The results indicate that chain length and penultimate unit effects are extremely important during the early stages of the polymerisation process. In the case of the attacking radical (i.e., R• in: R• + SC(Z)SR′ → RSC•(Z)SR′), the equilibrium constant varies by over three orders of magnitude on extending R• from the styryl unimer to the trimer species and actually increases with chain length, further confirming that K is high in this system. When the reactions of the cumyl leaving group and cyanoisopropyl initiating species, which are also present in CDB‐mediated polymerisation of styrene in the presence of the initiator 2,2′‐azoisobutyronitrile, are also included, the variation in K extends over five orders of magnitude. Although less significant, the influence of the R′ group should also be taken into account in a complete kinetic model of the RAFT process. However, for most practical purposes, its chain length effects beyond the unimer stage may be ignored. These results indicate that current simplified models of the RAFT process, which typically ignore all chain length effects in the R and R′ positions, and all substituent effects in the R′ position, may be inadequate, particularly in modelling the initial stages of the process. magnified image

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Section: Discussionmentioning

confidence: 99%

Is the Addition‐Fragmentation Step of the RAFT Polymerisation Process Chain Length Dependent?

Izgorodina

Coote

2006

Macro Theory & Simulations

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“…If a monomer appears in parentheses relatively poor control was reported (usually manifest as a broad molecular weight distribution (PDI > 1.4) and/or significant retardation/inhibition Size exclusion chromatography coupled to electrospray ionization mass spectrometry has been used to characterize RAFT-synthesized PMA. [136] The work is described below under Side Reactions in RAFT. GPC coupled with UV detection has been used to determine the butyl trithiocarbonate and phthalimidomethyl ends groups of PBA prepared with RAFT agent 62.…”

Section: Characterization Of Raft-synthesized Polymersmentioning

confidence: 99%

“…As in previous studies of this nature, these were not detected. [136] Buback and Vana [144] have proposed a new mechanism for disappearance of the product of intermediate radical termination during RAFT polymerization with dithiobenzoates. In that it does not lead to byproducts and the proposal has the potential of resolving the current impasse re the mechanism of retardation observed in these polymerizations.…”

Section: Side Reactions In Raft Polymerizationmentioning

confidence: 99%

Living Radical Polymerization by the RAFT Process—A First Update

Moad¹,

Rizzardo²,

Thang³

2006

Aust. J. Chem.

859

787

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This paper provides a first update to the review of living radical polymerization achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of Reversible Addition-Fragmentation chain Transfer (RAFT) published in June 2005. The time since that publication has witnessed an increased rate of publication on the topic with the appearance of well over 200 papers covering various aspects of RAFT polymerization ranging over reagent synthesis and properties, kinetics, and mechanism of polymerization, novel polymer syntheses, and diverse applications.

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“…70 More recently, Barner-Kowollik and coworkers have investigated acrylate polymerizations with the aim of comprehensively mapping their product distribution spectrum via ESI-MS in linear 71,72 as well as in living (RAFT) complex architecture formation processes. 39,73 In the following, we will highlight some of the key findings derived from these studies. One of the main difficulties in studying the product spectrum of polymers via ESI-MS mass spectrometry is the fact that high-resolution spectra can typically only be obtained for mass to charge ratios, m/z, of below 2000.…”

Section: Mass Spectrometry Of Acrylate Polymersmentioning

confidence: 99%

The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

Junkers

Barner‐Kowollik

2008

J. Polym. Sci. A Polym. Chem.

213

326

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The past 5 years have seen a significant increase in the understanding of the fate of so‐called mid‐chain radicals (MCR), which are formed during the free radical polymerization of monomers that form highly reactive propagating radicals and contain an easily abstractable hydrogen atom. Among these monomers, acrylates are, beside ethylene, among the most prominent. Typically, a secondary propagating acrylate‐type macroradical (SPR) can easily transfer its radical functionality via a six‐membered transition state to a position within the polymer chain (in a so‐called backbiting reaction), creating a tertiary MCR. Alternatively, the radical function can be transferred intramolecularly to any position within the chain (also forming an MCR) or intermolecularly to another polymer strand. This article aims at providing a comprehensive overview of the up‐to‐date knowledge about the rates at which MCRs are formed, their secondary reactions as well as the consequences of their occurrence under variable reaction conditions. We explore the latest aspects of their detection (via electron spin resonance spectroscopy) as well as the characterization of the polymer structures to which they lead (via high resolution mass spectrometry). The presence of MCRs leads to the formation of branched polymers and the partial formation of polymer networks. They also limit the measurement of kinetic parameters (such as the SPR propagation rate coefficient) with conventional methods. However, their occurrence can also be used as a synthetic handle, for example, the high‐temperature preparation of macromonomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7585–7605, 2008

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An in-depth analytical approach to the mechanism of the RAFT process in acrylate free radical polymerizations via coupled size exclusion chromatography–electrospray ionization mass spectrometry (SEC–ESI-MS)

Cited by 85 publications

References 50 publications

Is the Addition‐Fragmentation Step of the RAFT Polymerisation Process Chain Length Dependent?

Is the Addition‐Fragmentation Step of the RAFT Polymerisation Process Chain Length Dependent?

Living Radical Polymerization by the RAFT Process—A First Update

The role of mid‐chain radicals in acrylate free radical polymerization: Branching and scission

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